AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 510 AM EDT SAT JUL 9 2011 .SYNOPSIS... SHOWERS AND ISOLATED THUNDERSTORMS WILL DEPART QUICKLY THIS MORNING AS A LOW PRESSURE MOVES FARTHER AWAY FROM SOUTHERN NEW ENGLAND. HIGH PRESSURE THEN BRINGS DRIER AIR ACROSS NEW ENGLAND FOR THIS WEEKEND. A COLD FRONT WILL MOVE SLOWLY THROUGH THE REGION LATE MONDAY THROUGH TUESDAY...BRINGING A CHANCE OF SHOWERS AND THUNDERSTORMS. HIGH PRESSURE RETURNS WEDNESDAY INTO THE END OF THE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... BASED ON LATEST RADAR TRENDS...00Z NAM IS TOO SLOW TO MOVE PRECIPITATION OUT THIS MORNING. FAVORED A BLEND OF THE 00Z GFS AND 08/21Z SREF INSTEAD. 09/04Z HRRR TIMING OF RAINFALL WAS ABOUT TWO HOURS TO SLOW...BUT THE LOCATION WAS EXCELLENT. TIME-SHIFTED THAN GUIDANCE TO PROVIDE TIMING TO END OF SHOWERS. WITH THE GFS THE FAVORED MODEL OVER THE NAM...STAYED CLOSER TO THE MAV GUIDANCE FOR TEMPERATURES. AFTER LOOKING AT LATEST OBSERVED SWELL HEIGHTS AND PERIODS... DECIDED TO ISSUE A STATEMENT HIGHLIGHTING THE HIGH RISK OF RIP CURRENTS ALONG THE SOUTH-FACING BEACHES OF THE VINEYARD AND NANTUCKET. CONTEMPLATED A HIGH SURF ADVISORY...BUT DO NOT THINK THE SURF WILL GET HIGH ENOUGH TO MEET THAT CRITERIA. THIS WILL NEED TO BE MONITORED BY THE NEXT SHIFT. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... HIGH PRESSURE TAKES MORE CONTROL OF OUR WEATHER TONIGHT INTO SUNDAY. TEMPERATURES LOOK TO BE QUITE SEASONABLE. COULD SEE PATCHY FOG DEVELOP THIS EVENING NEAR NANTUCKET FOR A TIME UNTIL THE DRIER AIR CAN GET FULLY ESTABLISHED. GOOD RADIATIONAL CONDITIONS COULD ALSO RESULT IN PATCHY FOG ACROSS PORTIONS OF THE CT RIVER VALLEY BETWEEN KEENE NH AND ORANGE MA. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... MAIN POINTS... *MILD MONDAY WITH POSSIBLE AFTERNOON CONVECTION *SHOWERS AND THUNDERSTORMS ALONG A COLD FRONT EXPECTED TUESDAY *UNSEASONABLY COOL FOR WEDNESDAY AND THURSDAY *MORE SUMMER-LIKE WEATHER FOR FRIDAY AND PSBLY THE WEEKEND OVERVIEW... FELT THE 0Z NAM WAS POORLY HANDLING THE PRESENT SITUATION AND FELT BETTER CONFIDENCE WITH THE 0Z GFS WHICH HAS BEEN FAIRLY CONSISTENT THE LAST FEW RUNS IN HANDLING THE OVERALL TRENDS...ALONG WITH THE 12Z ECMWF. FELT A BLEND OF THE MAV/GFS ALONG WITH MOS GUIDANCE WAS WARRANTED FOR THE FCST PD. DETAILS... SUNDAY NIGHT INTO MONDAY... A COOL EVNG FOR SUNDAY NIGHT WITH LGT/VRB SLY FLOW. MAY SEE THE INCREASE OF MID-LVL CLOUDS OVERSPREAD THE RGN AHEAD OF THE ONCOMING SYNOPTIC SYS FOR TUESDAY. AS FOR MONDAY...ANTICIPATE PARTLY CLOUDY CONDITIONS WITH CONVECTION PSBL TOWARDS AFTN. UNCERTAIN WHETHER THIS CONVECTION IS A RESULT OF A LEE TROF AHEAD OF TUESDAYS COLD FRONT... OR RATHER ISENTROPICALLY FORCED ALONG AND AHEAD OF A MID-LVL THERMAL RIDGE ADVECTING OUT OF THE SW. ASIDE...MARGINAL SHEAR EVIDENT WITH 0-6KM VALUES OF 30 TO 40 KTS WITH VECTORS ORTHOGONAL TO A PSBL LEE TROF...AN INDICATION OF POTENTIALLY SEEING DISCREET MULTI-CELLULAR CONVECTION. INSTABILITY WILL BUILD ALONG WITH THE INFLUX OF WARM/ MOIST AIR VIA MODEST SW FLOW...GUSTING AT TIMES AT THE SFC...ALONG AND AHEAD OF THE AFOREMENTIONED SYNOPTIC SYS. YET WARM AIR AT H85 MAY ACT TO CAP SFC DESTABILIZATION AND RESULT IN ELEVATED CONVECTION...DEPENDENCE ON MOISTENING AT THE SFC WHICH FEEL PERHAPS THE FAVORABLE GFS IS TOO ROBUST. HAVE CHC POPS FOR NOW WITH A BLEND OF A FEW DEGREES ABOVE MAV/MOS GUIDANCE FOR TEMP AND DEW POINTS. MONDAY NIGHT INTO TUESDAY... EXPECT CONVECTION TO LIFT ENEWD AND GRADUALLY DISSIPATE INTO A LESS FAVORABLE AIRMASS...WILL LIKELY SEE A LULL INTO MONDAY NIGHT WITH CLOUDS KEEPING OVRNGT MINS MILD. INTO TUESDAY SFC COLD FRONT DRAGS THRU THE RGN WITH A GOOD CHC FOR SHOWERS AND TSTORMS. STILL SOME QUESTION CONCERNING WHETHER CONVECTION WILL BECOME SFC-BASED... LINGERING CLOUDS FROM PREV DAY CONVECTION...AS WELL AS WEAK ISENTROPIC LIFT OF RICH THETAE AIR COULD LEND TO MID-LVL CLOUDS OVERSPREADING THE RGN. ASIDE...MID-LVL MOISTENING AND SUBSEQUENT COOLING WILL LEND TO SUBSTANTIAL ELEVATED INSTABILITY. CONTINUED MODEST SHEAR ORTHOGONAL TO THE FRONTOGENETICALLY FORCING SFC COLD FRONT...PARENT WITH ENHANCED ASCENT AS THE MAIN SHRTWV ENERGY DIGS THRU N NEW ENGLAND...SHOULD PROVIDE THE POSSIBILITY FOR DISCREET CONVECTION ACROSS THE FCST RGN. UNCERTAIN AS TO THE SEVERITY OF WHICH...BUT CONFIDENT ENOUGH TO USHER SOME CONCERN OF POTENTIAL THREATS. ANTICIPATE AS WE GET CLOSER TO TUESDAY THERE SHOULD BE A BETTER HANDLE. CONTINUED WITH MAV/MOS GUIDANCE GOING A FEW DEGREES HIGHER FOR TEMPS. TUESDAY NIGHT INTO WEDNESDAY... ADDITIONAL ENERGY WILL ROTATE THRU NEW ENGLAND ON THE BACKSIDE OF THE DEPARTING LOW ACROSS E CANADA. ENHANCED ASCENT/CYCLONIC FLOW OF RESIDUAL MOISTURE ON THE BACKSIDE...COUPLED WITH COOLING AT MID-LVLS...WILL LIKELY LEND TO MID-LVL CLOUDS TO STREAM THRU THE EVNG PD...AND DIURNAL CU TO DEVELOP DURING THE DAY. WILL SEE THE USHERANCE OF UNSEASONABLY COOL AIR AS A SECONDARY COLD FRONT ASSOC WITH THE AFOREMENTIONED ADDITIONAL ENERGY SLIDES THRU THE RGN. WEDNESDAY NIGHT TOWARDS THE WEEKEND... UNSEASONABLY COOL. WILL SEE SOME VERY CHILLY EVENINGS FOR WEDNESDAY AND THURSDAY NIGHT AS LGT/VRB FLOW COUPLED WITH CONTINUED CAA AT MID-LVLS...AND MOSTLY CLEAR CONDITIONS...WILL LEND TO TEMPS IN THE LOW TO MID 50S FOR MINS. WOULD NOT BE SURPRISED TO SEE LOCALES AT HIGHER ELEVATIONS REPORT UPR 40S. DURING THE DAY...ALBEIT ABUNDANT SUNSHINE...THE COOLER AIR MASS ENTRENCHED OVER THE RGN MAY KEEP MAX TEMPS FEELING MORE LIKE LATE SPRING FOR THURSDAY. YET BY FRIDAY THE SFC HIGH SHOULD MOVE OFFSHORE AND RETURN SLY FLOW SHOULD BEGIN TO WARM CONDITIONS ACROSS THE RGN TO MORE SUMMER-LIKE...SEASONABLE... CONDITIONS. MAY SEE ANOTHER SYSTEM INTO THE WEEKEND...BUT THIS DEPENDENCE RELIES ON THE NATURE OF THE DEPARTING SFC HIGH. AT THIS POINT GFS/ECMWF ARE INCONSISTENT ON THE OUTCOME...SO LOW CONFIDENCE IN THE FCST FOR THE WEEKEND. && .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT MODERATE...30 PERCENT TO 60 PERCENT HIGH...GREATER THAN 60 PERCENT THROUGH 12Z...CHAOTIC CONDITIONS EARLY THIS MORNING...RANGING FROM VFR TO VLIFR. VERY DIFFICULT TO NAIL DOWN THE TIMING AT SPECIFIC LOCATIONS. TRENDS ARE VERY CLEAR THOUGH...WITH IMPROVEMENT TO VFR FROM WEST TO EAST STARTING IN EARNEST DURING THE PRE-DAWN HOURS. TODAY AND TONIGHT...HIGH CONFIDENCE VFR MOST LOCATIONS. POSSIBLE LINGERING IFR IN FOG ACROSS CAPE COD AND THE ISLANDS THROUGH MID- MORNING. PATCHY IFR IN FOG COULD REDEVELOP FOR A TIME THIS EVENING NEAR KACK...BUT ONLY MEDIUM CONFIDENCE. SUNDAY...HIGH CONFIDENCE VFR. KBOS TERMINAL...LOW TO MEDIUM CONFIDENCE IN FIRST 6 HOURS OF TAF. HIGH CONFIDENCE AFTER THEN. OUTLOOK...SUNDAY THROUGH WEDNESDAY... SUNDAY NIGHT... HIGH CONFIDENCE VFR. MID-LVL CLOUDS MAY OVERSPREAD ACROSS THE RGN WITH LGT/VRB SLY FLOW. CANT RULE OUT THE POSSIBILITY FOR FOG IMPACTS ACROSS THE SOUTHEAST TERMINALS ALONG THE CAPE/ISLANDS...LOW CONFIDENCE AT THIS TIME. MONDAY INTO TUESDAY... MEDIUM CONFIDENCE VFR/MVFR. COLD FRONT TO APPROACH INTO TUESDAY ALONG AND AHEAD OF WHICH SHRA/TSRA WILL BE POSSIBLE BEGINNING DURING THE MONDAY AFTN PD W TO E. WILL SEE SW FLOW GUSTING AT TIMES. ANY SHRA/TSRA IMPACTING THE TERMINALS MAY LEND TO TEMPO IFR/LIFR IMPACTS. COULD SEE PSBL IFR/LIFR FOG IMPACTS DURING THE EVNG PDS ALONG THE SE TERMINALS. WEDNESDAY... HIGH CONFIDENCE VFR. N/NW FLOW BECOMING LGT/VRB. && .MARINE... INCREASING SOUTH SWELLS SHOULD BUILD SEAS TO 4 TO 7 FT ACROSS THE OUTERMOST COASTAL WATERS. THESE SWELLS PEAK THIS AFTERNOON INTO THIS EVENING...THEN GRADUALLY DIMINISH THROUGH SUNDAY MORNING. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... SUNDAY NIGHT... SEAS AND WINDS TO REMAIN BELOW SCA THRESHOLDS. MONDAY INTO TUESDAY... SEAS TO BUILD ABOVE 5 FEET FOR THE S/SE OPEN WATERS IN ACCORDANCE WITH STRONG SW FLOW GUSTING AT TIMES POSSIBLY AS HIGH AS 25 KTS. CONFIDENCE IS SOMEWHAT LOW ON THE SPECIFICS...BUT FEEL SCA THRESHOLDS WILL BE MET. SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE ACROSS THE WATERS BEGINNING AROUND MONDAY EVENING. WEDNESDAY... WINDS AND SEAS TO DISSIPATE. MAY SEE SOME GUSTS AROUND 15 KTS BEHIND THE DEPARTING COLD FRONT INTO WEDNESDAY. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...RIP CURRENT RISK THROUGH THIS EVENING FOR MAZ023-024. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 6 AM EDT SUNDAY FOR ANZ237. SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 8 AM EDT SUNDAY FOR ANZ235-254. SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL NOON EDT SUNDAY FOR ANZ255-256. && $$ SYNOPSIS...BELK/SIPPRELL